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Out of the box it's pretty clear ARKit doesn't allow for the tracking of more than 4 images at once. (You can "track" more markers than that but only 4 will function at a time). See this question for more details on that.

However, I'm wondering if there is a possible work-around. Something like adding and removing anchors on a timer or getting the position information and then displaying the corresponding models without ARKit, etc. My knowledge of Swift is fairly limited so I haven't had much luck experimenting yet. Any suggestions or pointers in the right direction would be helpful.

By comparison ARCore for Android has a limit of 20 according to the documentation. I've also personally tested web based libraries tracking over 4 markers on an iPhone. I also believe I read somewhere that some variation of the Nintendo DS was able to track more than 4 markers. There is no way this isn't feasible because of hardware limitations.

Andy Jazz
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iicaptain
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1 Answers1

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ARKit 5.0

Today's answer is YES, you can. Apple has told that developers can now detect up to 100 images at a time in ARKit 5.0 announced at WWDC 2021. Let's check this out.

ARKit 4.0

There's no workaround in ARKit 4.0 to simultaneously track more than FOUR images using ARImageAnchor subclass inside session's ARImageTrackingConfiguration(). I should say that this limitation works despite the fact that the total number of tracked images in a scene can be up to 100 in ARKit 4.0.

You can read comments in ARConfiguration class if you choose Jump to Definition option.

enter image description here

I believe this feature was limited by Cupertino software engineers not occasionally. ARImageAnchor subclass inherits from ARAnchor parent class and conforms to ARTrackable protocol, so it tracks not only static images but moving images as well (like a logo on a car's body). Hence, if you track more than 4 images – it's highly CPU/GPU intensive (the most notorious thing for draining phone's battery), cause your device must detect and track several different objects.

I suppose it will be possible to simultaneously track more than 4 images with a newer ARKit 4.0 version that can be run on considerably powerful 5nm devices, like iPhone 12, that we'll see this fall.

Thus, Apple software engineers sacrificed apps functionality for the sake of a robust AR experience.

P.S.

It is incorrect to compare ARCore with ARKit, 'cause these frameworks work differently inside, even though they have similar fundamental principles – like World Tracking, Scene Understanding and Rendering stages. And in addition to the above, I should say that ARCore has more modest functionality than ARKit, which makes ARCore more "lightweight" for CPU calculations (although I understand that the last phrase sounds very subjective).

Andy Jazz
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  • "I suppose you can track 4+ images with 5nm devices, seemingly in late 2020." - can you expand on this? Also I completely understand that performance and battery drain would be bad but it's frustrating that Apple is taking that choice away from the dev. – iicaptain Jan 30 '20 at 13:39
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    Devices with A14 chipset will be considerably powerful than existing ones. And for Apple it's much more frustrating if user's AR experience lasts just several minutes instead of an hour, at least. And don't forget – overheating kills battery. – Andy Jazz Jan 30 '20 at 13:44